1. Field of the Invention
This invention relates to molding die apparatus. In one of its aspects, the invention relates to a die frame assembly wherein improved guide means reciprocably support an ejector assembly for ejecting molded parts from a mold cavity.
2. State of the Prior Art
In injection molding equipment, die frame assemblies have means for ejecting the molded parts from a movable mold half as the mold is moved away from a stationary mold half. A movable ejector assembly is mounted reciprocably on the movable die frame and includes ejector pins which extend through the mold half. The movable ejector assembly also includes return pins which extend through the die frame to return the ejector assembly to retracted position upon closing of the mold. Holes in the frame and the die and the pins must be made with great precision to avoid binding of the pins or undue friction of the pins during movement of the ejector assembly. Nevertheless, even with close tolerances, some binding and wearing of the holes and pins occur. The wearing and binding introduce looseness or "slop" of the ejector assembly within the die frame, thereby causing accelerated wear and binding of the ejector assembly in the frame. Continued wear and binding can cause premature failure of the die and/or breakage of the pins.
One solution to this problem has been to amount guide pins on the frame with the guide pins extending through the base or clamp plate of the die frame and through the ejector plate or master ejector plate in the ejector assembly. The master ejector assembly is thus guided on the guide pins. With the ejector assembly guided by the guide pins, excessive wear on the holes for the ejector and return pins is minimized.
The guide pin or leader pin, as it is known, is a significant improvement over using the holes in the frame and the mold to guide the ejector assembly. However, this guide system is still relatively expensive as it requires extensive precision machining to assure proper fit between the guide pins and the ejector assembly.